24VDC digital inputs are widely used in PLCs (Programmable Logic Controllers) for several reasons:

1. Compatibility: Many industrial sensors, switches, and actuators operate on a 24VDC power supply, making 24VDC digital inputs compatible with a wide range of field devices commonly used in industrial automation applications.

2. Standardization: 24VDC digital inputs have become a standard in industrial automation due to their widespread adoption and compatibility with various PLCs and field devices. This standardization simplifies system integration and interoperability.

3. Reliability: 24VDC digital inputs offer reliable operation in harsh industrial environments, withstanding voltage fluctuations, electromagnetic interference (EMI), and temperature variations commonly encountered in manufacturing facilities and industrial settings.

4. Safety: Low-voltage DC signals, such as 24VDC, are considered safer than higher-voltage signals, reducing the risk of electric shock and ensuring compliance with safety regulations in industrial environments.

5. Ease of Wiring: 24VDC digital inputs typically require simpler and less expensive wiring compared to higher-voltage inputs, reducing installation costs and complexity.

6. Power Efficiency: Operating at a lower voltage (24VDC) helps reduce power consumption and heat generation in PLC systems, contributing to energy efficiency and minimizing thermal stress on components.

7. Scalability: 24VDC digital inputs can be easily expanded or added to PLC systems to accommodate changes in system requirements or the addition of new field devices, providing scalability and flexibility in system design.

8. Cost-Effectiveness: 24VDC digital inputs are cost-effective solutions for industrial automation applications, offering a balance between performance, reliability, and affordability compared to higher-voltage alternatives.

Overall, the widespread use of 24VDC digital inputs in PLCs is driven by their compatibility, reliability, safety, ease of wiring, power efficiency, scalability, and cost-effectiveness, making them well-suited for a wide range of industrial automation applications.